MOSCOW, Feb 19 (Reuters) - Russian businessman Mikhail Prokhorov has agreed to sell a 6 percent stake in Russian aluminium giant Rusal to a consortium of investors led by billionaire Viktor Vekselberg and his partners, the consortium said on Monday.

The sale will close a chapter at the world’s second largest aluminium producer. Prokhorov’s purchase of a stake in Rusal triggered a long-running battle for control of mining giant Norilsk Nickel 10 years ago.

The consortium said in a statement that after the deal, Vekselberg and his partners will hold 26.5 percent in Hong Kong-listed Rusal. It did not provide any further detail about the deal.

Rusal has a market value of almost $11 billion, according to Thomson Reuters Eikon.

Onexim group, which manages Prokhorov’s assets, and En+ Group, a company controlled by Russian businessman Oleg Deripaska which owns 48 percent of Rusal, declined to comment. Rusal and Vekselberg’s main investment vehicle, Renova, did not provide an immediate comment.

The sale will reduce Prokhorov’s share in Rusal to zero.

He acquired a stake in the company in 2008 when Onexim sold Rusal a blocking stake in Nornickel, a major global nickel and palladium producer, fuelling a power battle between Rusal and Nornickel’s other shareholder, Vladimir Potanin.

This power struggle over Nornickel resurfaced on Friday as billionaire Potanin offered to buy Chelsea soccer club owner Roman Abramovich’s stake in the mining group, and Deripaska tried to block the deal.

It was not clear whether Vekselberg was trying to boost his influence in Rusal by buying the remaining stake from Prokhorov, while Deripaska is fighting for Nornickel.

Prokhorov has been gradually reducing his presence in the Russian business since Russian law enforcement officials searched offices of his Onexim group two years ago, saying that the searches were related to a tax investigation at an unspecified firm or group.

At the time, two sources told Reuters they believed the searches were linked to Prokhorov’s RBC media holding, which had published revelations about people with ties to President Vladimir Putin. The Kremlin has denied this link.

Prokhorov later sold RBC media and started gradually reducing the stake in Rusal. He still owns some financial assets and a power generator Quadra but they are not as big as Rusal. (Reporting by Polina Devitt; editing by Adrian Croft)